1. Field of the Art
This invention relates to a valved plug for an endoscopic biopsy channel, and more particularly to a valved plug to be detachably fitted on a mouth piece at an entrance opening to a biopsy channel, which is provided on medical endoscopes for introduction of forceps or other biopsy and surgical instruments.
2. Prior Art
Generally, medical endoscopes which are introduced in a body cavity for examination or therapeutic purposes are largely constituted by a manipulating head assembly to be gripped in an operator's hand for manipulating of various control means, an insertion tube extended out on the front side of the manipulating head assembly, and a universal cable which is led out on the rear side of the manipulating head assembly for connection to a light source etc. Along with an endoscopic image pickup means, an illumination window or windows are provided in a casing of a tip end section at the fore distal end of the insertion tube to project illumination light toward an intracavitary site under examination.
For example, in case a diseased portion is spotted as a result of an endoscopic examination, it may become necessary to give a certain treatment to the diseased portion or to get tissue samples therefrom. Therefore, for this purpose, many endoscopes are provided with the so-called biopsy channel to permit introduction of forceps or other biopsy or surgical instruments therethrough. The biopsy channel is coextensively extended through the insertion tube of the endoscope toward an outlet opening which is provided on the casing of the distal tip end section along with the illumination and endoscopic image pickup means. A biopsy or surgical instrument is introduced into the biopsy channel through an inlet opening which is provided in the casing of the manipulating head assembly or at a joint portion of the insertion tube and the manipulating head assembly.
Partly because the pressure within a body cavity is higher than the atmospheric pressure and partly because the biopsy channel is also utilized as a suction passage, the inlet opening of the biopsy channel cannot be left in an open state. Therefore, it is the general practice to close the inlet opening of the biopsy channel with a plug, by fitting the plug on a mouth piece which is provided around the inlet opening. An instrument can be introduced into the biopsy channel without removing the plug from the mouth piece. Namely, the plug is provided with an on-off valve in its internal passage, which can be pushed open when an instrument is introduced into the biopsy channel. Nevertheless, since it is necessary to wash clean the interior of the biopsy channel each time after use, the plug is normally detachably fitted on the mouth piece of the biopsy channel.
Instrument to be introduced into a body cavity by way of the biopsy channel on an endoscope vary over a certain range in diameter, from forceps with relatively large outside diameters to narrow tubes with extremely small diameters. In other words, an endoscopic biopsy channel is used for introduction of instruments of diversified outside diameters. Ideally, the on-off valve to be provided in the plug should be capable of holding the circumference of an inserted instrument tightly in a sealed state. However, there have never been developed biopsy channel plugs which can maintain perfect air tightness around the circumference of various thick and narrow instruments which greatly differ in outside diameter, for example, perfect air tightness around a thick instrument which is almost as large as the diameter of the inlet opening of the biopsy channel as well as around a narrow instrument which is far smaller in diameter.
As for conventional biopsy channel plugs of the sort mentioned above, it has been widely known in the art to provide within a plug a constricted passage of a diameter smaller than the inlet opening of the biopsy channel and to provide a slit of a length equivalent with or larger than the diameter of the inlet opening in such a way that the slit is normally closed to maintain the inlet opening of the biopsy channel substantially in a hermetically closed state. The slit is pushed open upon introducing an instrument into the inlet opening of the biopsy channel. In the case of a narrow instrument, it is relatively easy to maintain air tightness because the slit is opened only in a small degree. On the contrary, when a thick instrument is introduced into the biopsy channel, the slit is opened wide to such a degree as to brake its air tightness. However, since the constricted passage is provided in addition to the slits, the thick instrument spreads the constricted passage radially outward as it is introduced into the biopsy channel, and walls of the constricted passage tightly fit around the inserted instrument to form a hermetical seal therearound. Therefore, while an instrument is introduced into a body cavity through the biopsy channel for a biopsy or surgical treatment, there is little possibility of body fluids flowing in a reverse direction and coming out through the inlet opening of the biopsy channel and depositing on the manipulating hand of the operator.
In this connection, there has been known in the art a plug construction which has the above-mentioned constricted passage and slit valve on one and same structure, for example, from Japanese Patent Publication H5-57848. More specifically, in the case of the Japanese Patent Publication just mentioned, the biopsy channel plug is composed of a tubular main body portion internally provided with a constricted passage and adapted to be fitted on a mouth piece at the entrance opening of a biopsy channel, and a lid member containing a slit as an on-off valve and connected with the main body portion through a flexibly foldable connecting strip. In use, firstly one end of the main body portion of the plug is fitted on the mouth piece of the biopsy channel entrance opening, and then the valved lid member is fitted in the other outer end of the main body portion.
The main body and the valved lid member of the plug are separably coupled with each other. In this regard, it is important for the main body portion and the valved lid member to be able to maintain hermetical tightness when coupled with each other. Therefore, in the case of the above-mentioned Japanese patent publication, an inwardly projecting annular brim is provided at the outer end of the main body portion. The annular brim is adapted to be trapped in an annular groove which is provided on the side of the valved lid member, when the valved lid member fitted into the main body portion of the plug. At this time, the inner periphery of the annular brim is abutted against the bottom of the annular groove to form a hermetical seal therebetween. The annular brim is formed in a thickness which is smaller than the width of the annular groove on the side of the lid member. Further, the lid member is formed with a flanged portion around its inner end to be fitted into the main body portion. On the other hand, an axially projecting annular ridge is provided on a partition wall around a constricted passage in such a way that the flange portion at the inner end of the lid member is gripped between the annular ridge and a lower surface of a wall portion which defines the annular trapping groove. Accordingly, the brim portion which is projected radially inward at the outer end of the main body portion is abutted against bottom surfaces and inner rising wall portions of the annular groove, but it is left out of contact with outer rising wall portions of the trapping groove.
By the way, among endoscopically inserting instruments of various sizes, an instrument of large diameter forcibly tends to spread the constricted passage radially outward upon introduction into the biopsy channel through the slit in the lid member of lid portion of the plug. At this time, the lid portion of the plug is pressed against the axially projecting ridge on the partition wall, and therefore it is retained in the coupled state without receiving adverse effects in this regard. However, when the thick instrument is extracted from the biopsy channel, the partition wall around the constricted passage is pulled and displaced in an upward direction. As a consequence, the lid portion of the plug is pushed by the axial ridge portion on the partition wall in a direction of separating same from the main body of the plug. The brim portion which is provided at the outer end of the main body portion is abutted against the inner rising wall portion of the annular groove on the side of the lid member, so that it acts to restrict movements of the lid portion. Namely, at the time an instrument is extracted from the biopsy channel, the force acting to separate the lid portion from the main body portion of the plug is sustained by the inwardly projecting brim portion which is provided at the outer end of the main body portion. Besides, since the top side of the brim portion in put in a free state and the axial ridge portion is located radially inward of the brim portion, the force acting to push up the lid portion through the brim portion is amplified by a degree which corresponds to a positional differential between the projected portion and the rim portion.
Therefore, the inwardly protruding brim portion at the outer end of the main body portion can be deformed into an outwardly bent form by repeated insertions and extractions of instruments, and as a result lid gripping force of the brim portion can be gradually deteriorated. In such a state, if an instrument is inserted into the biopsy channel through the plugged inlet opening and then abruptly extracted out of the plug, the lid portion of the plug can be unintentionally separated from the main body portion because the brim portion on the main body portion no longer has sufficient lid holding force. Further, as mentioned hereinbefore, the biopsy channel also serves for use as a suction passage. When a suction valve on the manipulating head assembly of the endoscope is operated for aspiration and then closed to end the aspiration, the flow of aspirate fluids within the biopsy channel is stopped and the pressure within the biopsy channel is elevated to a relatively high level. This elevated pressure acts on inner surfaces of the lid portion of the plug. Therefore, in case the lid holding force of the brim portion on the main body portion has deteriorated to a material degree, the lid portion of the plug can be pushed off the main body portion by the internal pressure of the biopsy channel. In such a case, a large amount of aspirate can flow out through the biopsy channel plug and scatter around the operator.